description = [[
Spiders a web site to find web pages requiring form-based or HTTP-based authentication. The results are returned in a table with each url and the
detected method.
]]

---
-- @usage
-- nmap -p 80 --script http-auth-finder <ip>
--
-- @output
-- PORT   STATE SERVICE
-- 80/tcp open  http
-- | http-auth-finder: 
-- |   url                                   method
-- |   http://192.168.1.162/auth1/index.html  HTTP: Basic, Digest, Negotiate
-- |_  http://192.168.1.162/auth2/index.html  FORM
--
-- @args http-auth-finder.maxdepth the maximum amount of directories beneath
--       the initial url to spider. A negative value disables the limit.
--       (default: 3)
-- @args http-auth-finder.maxpagecount the maximum amount of pages to visit.
--       A negative value disables the limit (default: 20)
-- @args http-auth-finder.url the url to start spidering. This is a URL
--       relative to the scanned host eg. /default.html (default: /)
-- @args http-auth-finder.withinhost only spider URLs within the same host.
--       (default: true)
-- @args http-auth-finder.withindomain only spider URLs within the same
--       domain. This widens the scope from <code>withinhost</code> and can
--       not be used in combination. (default: false)

author = "Patrik Karlsson"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"discovery", "safe"}

require "httpspider"
require "shortport"
require "tab"

portrule = shortport.http

local function parseAuthentication(resp)
	local www_authenticate = resp.header["www-authenticate"]
	if ( not(www_authenticate) ) then
    	return false, "Server returned no authentication headers."
  	end
	
	local challenges = http.parse_www_authenticate(www_authenticate)
	if ( not(challenges) ) then
		return false, ("Authentication header (%s) could not be parsed."):format(www_authenticate)
	end
	return true, challenges
end


action = function(host, port)

	-- create a new crawler instance
	local crawler = httpspider.Crawler:new(	host, port, nil, { scriptname = SCRIPT_NAME } )

	if ( not(crawler) ) then
		return
	end

	-- create a table entry in the registry
	nmap.registry.auth_urls = nmap.registry.auth_urls or {}
	crawler:set_timeout(10000)

	local auth_urls = tab.new(2)
	tab.addrow(auth_urls, "url", "method")
	while(true) do
		local status, r = crawler:crawl()
		-- if the crawler fails it can be due to a number of different reasons
		-- most of them are "legitimate" and should not be reason to abort
		if ( not(status) ) then
			if ( r.err ) then
				return stdnse.format_output(true, ("ERROR: %s"):format(r.reason))
			else
				break
			end
		end

		-- HTTP-based authentication
		if ( r.response.status == 401 ) then
			local status, auth = parseAuthentication(r.response)
			if ( status ) then
				local schemes = {}
				for _, item in ipairs(auth) do
					if ( item.scheme ) then
						table.insert(schemes, item.scheme)
					end
				end
				tab.addrow(auth_urls, r.url, ("HTTP: %s"):format(stdnse.strjoin(", ", schemes)))
			else
				tab.addrow(auth_urls, r.url, ("HTTP: %s"):format(auth))
			end
			nmap.registry.auth_urls[r.url] = "HTTP"
		-- FORM-based authentication
		else
			-- attempt to detect a password input form field
			if ( r.response.body:match("<[Ii][Nn][Pp][Uu][Tt].-[Tt][Yy][Pp][Ee]%s*=\"*[Pp][Aa][Ss][Ss][Ww][Oo][Rr][Dd]") ) then
				tab.addrow(auth_urls, r.url, "FORM")
				nmap.registry.auth_urls[r.url] = "FORM"
			end
		end
	end
	if ( #auth_urls > 1 ) then
		local result = { tab.dump(auth_urls) }
		result.name = crawler:getLimitations()
		return stdnse.format_output(true, result)
	end
end